Creating a new site in a new version using a template exported from a previous version is recommended, but not required.
It's simple to make a new site using a previous version nod, by opening the nod and choosing to make a copy in the new version. Or just open the old nod in the new version, keeping in mind you can't go back.
I've done it hundreds of times over the years.
Copy your old version User Sites folder contents to your new version (of Fusion) User Sites folder.
Then open the nod in the new version site folder in User Sites using the new version.
You'll have to "refind" your site assets in Assets view, since the paths will be different, but that's it.